To the Editor:—In response to the comments of Drs. Moertel and Reitemeier, we wish to acknowledge the difficulty of evaluating a new agent in a small series of cases. We reported that three of 20 patients with gastrointestinal cancer responded to infusion of floxuridine. One of the patients initially received the agent as a two-hour infusion, and the following month was treated with the 24-hour infusion method, achieving a response to treatment subsequently.In an earlier study (Cancer Chemother Rep20:143, 1962), we reported tumor regression in two of eight patients with gastrointestinal carcinomas given floxuridine by rapid injection. Because of the small number of cases, we have refrained from stating percentage of responses since we felt that such values would have little statistical significance.Our aim was to report the minimal toxicity in relation to the observed benefit. In addition we endeavored to classify the cases according